Modular trocar system and methods of assembly

ABSTRACT

A modular trocar system is provided which includes an obturator assembly, and a cannula assembly defining a longitudinal passageway therethrough configured and dimensioned to slidably receive the obturator assembly, the cannula assembly including a housing which includes a valve assembly and a first mating portion, and a cannula defining a passageway of a predetermined dimension therethrough, the cannula including a second mating portion disposed thereon, the cannula and housing movable alternately between a spaced apart relative orientation and an attached orientation wherein the first and second mating portions are engaged. A method of assembly is also provided and includes the steps of connecting a shield member of a first predetermined configuration and dimension to a first housing section, attaching a knife blade assembly of a second predetermined configuration and dimension to the first housing section with a single motion wherein the attachment permits rotation of the knife blade relative to the first housing section, and attaching the first housing section to a second housing section with a quick connect mechanism which includes first and second mating portions such that the first and second housing sections are movable from a spaced apart position to a connected position in a single motion.

BACKGROUND

1. Technical Field

The present disclosure relates to trocar systems for inserting cannulasinto patients, and more particularly to modular trocar systems andmethods of assembly of trocar systems.

2. Background of Related Art

Minimally invasive surgical procedures where trocar systems aredesirable or even necessary are continually increasing in number andvariety. These procedures call upon surgeons to utilize an array ofvariously sized surgical equipment, e.g., graspers, dissectors, clipappliers, staplers, retractors, imaging systems, and the like.Accordingly, trocar assemblies having variously sized obturators andcannulas are required, e.g. 3-15 mm, to facilitate the range ofminimally invasive procedures while minimizing the size of each trocarentry to the extent possible.

Presently, placement of each different diameter cannula requires the useof a specially sized obturator assembly. In other words, to introduce a5 mm cannula, a 5 mm obturator is required; to introduce a 10 mmcannula, a 10 mm obturator is required; and so on. Manufacturers oftrocar assemblies must therefore produce and inventory numerousdifferent sized housings and operative components to allow themanufacture of each particular obturator and cannula variation to bemarketed. For obvious commercial reasons, health care providers andmedical equipment distributors of trocar assemblies must maintainappropriate inventories of each product variation to meet customerdemand as it arises.

WO 95/07663 to Vidal et al. discloses one approach to addressing thevariety of customer needs in the field of trocar assemblies. Vidal etal. disclose a plurality of obturator tips that are adapted to beremovably received by an obturator shaft, e.g., through a detent/leafspring arrangement or a lug/groove arrangement. While a variety ofcutting blade geometries are proposed from which the surgeon may select,each of the disclosed obturator tips is the same diameter so that thecompleted obturator assembly may be utilized with a cannula ofpreselected diameter.

It is also known to provide operative surgical instruments withinterchangeable working ends. For example, WO 94/13335 to Dorseydiscloses a "quick disconnect" arrangement for a suction/irrigationsystem that allows interchange between a variety of probes of differingshapes and orientation. See also U.S. Pat. No. 5,322,503 to Desai whichdiscloses an instrument that is adapted to receive a variety ofelectrostatic probes.

A further factor of significance in the design and use of trocar systemsis the ease with which the trocar system passes through the body wall soas to position the cannula thereacross. Thus, efforts have been expendedto minimize the penetration force of the trocar system while maintainingmaximum surgeon control and safety. U.S. Pat. No. 4,601,710 to Molldiscloses several trocar designs which include a spring biased safetyshield adapted to cover the cutting blade upon entry into the bodycavity. In one embodiment (see FIGS. 1-5B), the safety shield is slottedand the blade is configured to extend through the slots, therebyincreasing the effective diameter of the blade incision. See also U.S.Pat. No. 5,066,288 to Deneiga et al.

Despite these earlier efforts in the fields of interchangeability, aneed exists for a trocar system that is truly modular. That is, a trocarsystem wherein various is components thereof may be readilyinterchangeable and certain components standardized to facilitatemanufacture and use across a broader spectrum of product lines.

Moreover, improvements in trocar design which might minimize penetrationforce while maintaining surgeon control and safety during trocarpenetration are always warranted and to be welcomed.

SUMMARY

The present disclosure provides a modular trocar system which addresseslimitations associated with conventional manufacture and assembly oftrocar systems. The presently disclosed modular trocar system satisfiesthe need for greater inventory flexibility and management as well asachieving greater manufacturing efficiencies. In particular, thepresently disclosed modular trocar system permits utilization of some ofthe same components across many different sized trocar products. Thepresent disclosure also provides a modular trocar system which minimizespenetration force while maintaining surgeon control and providing anenhanced margin of safety during trocar entry.

One particular embodiment of the present disclosure provides a modulartrocar system which includes (i) an obturator assembly that includes anobturator, a knife and a safety shield movable with respect to theobturator and knife, and (ii) a cannula assembly defining a longitudinalpassageway therethrough configured and dimensioned to slidably receiveat least a portion of the obturator assembly. The cannula assemblyincludes a housing which includes a valve assembly and a first matingportion, and a cannula defining a passageway of a predetermineddimension therethrough, the cannula including a second mating portiondisposed thereon, the cannula and housing being movable between a spacedapart relative orientation and an attached orientation wherein the firstand second mating portions are engaged.

Preferably, a seal member is disposed between the housing and thecannula to provide a fluid-tight seal between the two elements.

In an alternative embodiment, a modular trocar system is provided whichincludes an obturator assembly that includes an obturator, a knife and ashield movable with respect to the obturator and knife, as well as ahousing having a first mating portion formed thereon. The safety shieldis defined by a shield member of a first predetermined configuration anddimension movably mounted with respect to the housing, and a knife bladeassembly of a predetermined configuration and dimension and having asecond mating portion formed thereon. The knife blade assembly isadapted to cooperate with the safety shield and preferably includes aknife and a distal shield member movably mounted with respect to theknife. The knife blade assembly is adapted to be attached to the housingwith a single motion.

A cannula assembly is also preferably provided which defines alongitudinal passageway therethrough configured and dimensioned toslidably receive at least a portion of the obturator assembly, thecannula assembly including a housing having a valve assembly disposedthereon and a cannula extending from the housing.

The knife assembly preferably includes a knife rotatably connected to arod with the second mating portion being formed on the rod. The knifepreferably has a circular base portion and a sharpened tip formed at adistal end of the base portion. Additionally, the knife may preferablyinclude a plurality of cutting edges which extend at least partiallyoutwardly from the circular base portion. The sharpened tip is formed bythe intersection of the plurality of cutting edges such that a planarsurface is formed and extends between each adjacent pair of cuttingedges over at least a portion of the length of the respective cuttingedges.

The knife assembly also preferably includes a distal shield member thatis movably mounted with respect to the knife. The distal shield memberpreferably includes a plurality of slots positioned to receivecorresponding cutting edges therewithin, and a plurality of inwardlytapered, substantially conical faces defined between adjacent slotswhich are adapted to interact with the corresponding planar surfacesdefined on the knife so as to minimize penetration force.

The present disclosure also provides a cannula assembly for use with atrocar system, the cannula assembly including (i) a housing whichincludes a valve assembly and a first mating portion and (ii) a cannuladefining a passageway of a predetermined configuration and dimensiontherethrough, the cannula including a second mating portion disposedthereon.

The cannula is preferably molded, having a substantially constant innerdiameter and an outer diameter that is gradually reduced in the distaldirection over its distal-most portion. For example, a preferred cannulaincludes a slightly larger inner diameter at its proximal end toaccommodate the introduction of instruments therein, e.g., of about 2-3cms length, and a gradually reduced outer diameter over the finalportion, e.g., about the distal-most 2-3 cms, to minimize penetrationforce. The remainder of the outer diameter of the cannula is preferablyconstant, thereby minimizing the likelihood that the cannula will pullout from the incision. The cannula and housing are preferably movablebetween a spaced apart relative orientation to an attached orientationwherein the first and second mating portions are engaged.

An obturator assembly is also provided in the present disclosure.Included in the obturator assembly are a housing including a firstmating portion, a shield member of a first predetermined configurationand dimension movably mounted with respect to the housing, a knife bladeassembly of a predetermined configuration and dimension and having asecond mating portion formed thereon and adapted to engage the firstmating portion such that the knife blade assembly is attached to thehousing with a single motion. The knife blade assembly preferablyincludes a knife and a distal shield member which is movably mountedwith respect to the knife, the distal shield member assuming an abuttingrelation with the shield member when the knife blade is assembly isattached to the housing.

A method of assembling an obturator assembly for use in a trocar systemis also provided and includes the steps of (i) mounting a shield memberof a first predetermined configuration and dimension to a first housingsection, (ii) mounting a distal shield member with respect to a knifeblade to define a knife blade assembly of a second predeterminedconfiguration and dimension, and (iii) connecting the knife bladeassembly to the first housing section with a single motion wherein theconnection permits rotation of the knife blade relative to the firsthousing section

A further method is provided for assembling a cannula assembly for usewith an obturator assembly as part of a trocar system, including thesteps of (i) aligning a first mating portion formed on a housing with asecond mating portion formed on a cannula which defines a passageway ofa predetermined size therethrough, (ii) moving the housing and thecannula from a spaced apart relative orientation to an attachedorientation, wherein the first and second mating portions are engaged,and (iii) forming a fluid-tight seal between the housing and thecannula. The housing preferably includes a valve assembly disposed in apassageway formed between an open proximal end and an open distal endthereof.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments are described herein with reference to the drawings,wherein:

FIG. 1 is a perspective view of one embodiment of the modular trocarsystem of the present disclosure;

FIG. 2 is a perspective view with parts separated of the modular trocarsystem of embodiment of FIG. 1;

FIG. 2A is an exploded perspective view, partially in section, showingfirst and second subassemblies of the modular trocar system;

FIG. 3 is a further perspective view of the embodiment of FIG. 1 withparts separated, which shows the obturator assembly components;

FIG. 4 is an enlarged view of the indicated area of detail of FIG. 3;

FIG. 4A is perspective view of an alternative knife blade for use withthe modular trocar system;

FIG. 5 is a plan view of the embodiment of FIG. 1, which shows the knifeshield in the retracted position;

FIG. 6 is a cross-section view taken along section line 6--6 of FIG. 5;

FIG. 7 is an enlarged view of the indicated area of detail shown in FIG.6;

FIG. 7A is a cross-section view taken along section line A13 A of FIG.7;

FIG. 8 is a cross-section view taken along section lines 813 8 of FIG.6;

FIG. 9 is an enlarged view of the area of detail indicated in FIG. 8;

FIG. 10 is a perspective view showing the distal end of the obturatorassembly and the knife shield;

FIG. 11 is a perspective view of the distal end of the modular trocarsystem embodiment of FIG. 1 showing the knife in a fully exposedposition;

FIG. 12 is a plan view of an alternate embodiment of the modular trocarassembly which shows the same sized proximally disposed componentsfitted with a larger sized knife and knife shield;

FIG. 13 is a cross-section view taken along section line 13--13 of FIG.12;

FIG. 14 is a perspective view with parts separated of the cannulaassembly of the embodiment of FIG. 1;

FIG. 15 is an enlarged view of the indicated area of detail of FIG. 14;

FIG. 16 is a perspective view of the cannula assembly valve housing;

FIG. 17 is an enlarged view of the indicated area of detail shown inFIG. 16; and

FIG. 18 is a further embodiment of the cannula assembly of the modulartrocar system of the present disclosure.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Referring initially to FIGS. 1 and 2, one embodiment of a modular trocarsystem in accordance with the present disclosure is designated byreference numeral 100 throughout the several views. Modular trocarsystem 100 is particularly adapted for use in minimally invasivesurgical procedures such as endoscopic or laparoscopic procedures.Generally, modular trocar system 100, when assembled into its twoprincipal subassemblies, includes an obturator assembly 110 and acannula assembly 112. The cannula assembly includes a valve assembly 114and a cannula 116, as described in detail further herein.

Except where noted otherwise, the materials utilized in the componentsof the presently disclosed modular trocar system generally includematerials such as either ABS or polycarbonate for housing sections andrelated components and stainless steel for components that are requiredto cut tissue. A preferred ABS material is CYCOLAC which is availablefrom General Electric. A preferred polycarbonate material is alsoavailable from General Electric under the trademark LEXAN. Analternative polycarbonate material which may be utilized is CALIBREpolycarbonate available from Dow Chemical Company. The polycarbonatematerials may be partially glass filled for added strength.

Referring now to FIG. 3, obturator assembly 110 includes an obturatorhousing 118 formed from housing base 119 and cylindrical housing cover120. Once the appropriate components are positioned therewithin (asdiscussed below), housing base 119 may be attached to cylindricalhousing cover 120 by engaging mating surfaces, for example by resilientlatches 122 formed on cover 120 interlocking with correspondingly shapedengaging surfaces 123 formed in the housing base 119. To uniformlyconnect base 119 and cover 120, preferably at least three correspondinglatches 122 and engaging surfaces 123 are provided and are spaced evenlyaround the circumference of cover 120 and housing base 119,respectively. Base 119 and cover 120 are preferably molded from an ABSmaterial and are preferably configured and dimensioned to functionallycooperate with various sizes of cannulas, e.g., 5-15 mm. Thus, obturatorhousing 118 is adapted to be a modular component for use with a widerange of trocar assemblies.

When fully assembled, obturator assembly 110 includes a safety shieldthat is movable with respect to knife blade 174 and that includes anelongated shield member 126 and a distal shield member 128, both ofwhich are preferably molded from a polycarbonate material. The distalend of elongated shield member 126 is provided with a reduced diameterportion 148 to define a shoulder 148a and to facilitate interaction withdistal shield member 128, as discussed below. Elongated shield member126 also includes proximal end portion 130 having a shield positionindicator, such as indicator post 132, extending transversely relativeto elongated shield member 126. Preferably post 132 is colored tocontrast sharply with the housing components. For example, indicatorpost 132 may be red if the housing components are white or lightcolored. Proximal end portion 130 further includes a transverse bearingsurface 134.

Elongated shield member 126 is disposed within a longitudinalthroughbore 136 formed through cylindrical extended portion 138 ofhousing base 119 with bearing surface 134 abutting housing base 119 on aproximal face thereof. Cylindrical extended portion 138 may be molded aspart of housing base 119 or, preferably, molded separately and mountedto housing base 119, e.g., by sonic welding. Cylindrical extendedportion 138 provides transverse support to the shield and obturatorcomponents that pass therethrough and preferably includes an inwardtaper at its distal end to facilitate passage through valve/sealassemblies. Abutment between transverse bearing surface 134 and housingbase 119 limits distal movement of shield member 126 relative thereto.Transverse bearing surface 134 also interacts with a guide rail 121molded within cover 120 (see FIG. 6) to assist in the angularorientation of shield member 126 relative to housing 118.

As best seen in FIGS. 6, 8 and 9, housing cover 120 preferably includesa distally directed, hollow cylindrical post 144 molded to the proximalface thereof. Although hollow post 144 serves several functions,initially it is noted that coil spring 140, which biases shield member126 toward a distal-most position through abutment with an annularflange 135 on shield member 126 (see FIG. 6), is positioned aroundhollow cylindrical post 144. Thus, hollow post 144 assists in alignmentof coil spring 140, e.g., to prevent kinking thereof. The diameter ofcoil spring 140 may be reduced in the region adjacent annular flange 135so as to fit snugly within proximal extension 142 of shield member 126.

Housing cover 120 is further provided with an open ended slot 146 toslidably receive position indicator post 132. Housing cover 120 mayfurther be provided with indicia (not shown) positioned adjacent openended slot 146 to provide additional visual indication to the user ofthe relative positioning of the shield, as is known in the art.

As noted above, the shield member 126 (and therefore the entire shieldmechanism) is biased in a distal-most position by coil spring 140. Alatching mechanism is provided to prevent proximal movement of theshield mechanism until such a time as obturator assembly 110 is insertedin a cannula assembly, e.g., cannula assembly 112, and the surgeon isprepared to begin trocar entry. The preferred latching mechanism issubstantially as described in commonly assigned U.S. Pat. No. 4,902,280to Lander, the entire contents of which are incorporated herein byreference.

Briefly, the latching mechanism includes a latch member 150 having twoleg portions 152 and 154. Latch member 150 is securely mounted tohousing base 119 through interaction between leg portion 152 and bracket156, and further interaction between the U-shaped portion of latchmember 150 and molded receiving portion 158. Leg portion 154 isresiliently flexible toward and away from leg portion 152. In a relaxedcondition, leg portion 154 is spaced away from leg portion 152 such thatextended portion 160 contacts abutment surface 134a (see FIG. 6) ofelongated shield member 126 to inhibit proximal movement thereof. Legportion 154 is further provided with extended resilient finger 162 whichabuts a ridge 164 formed in release member 166 which is movably mountedrelative to housing base 119.

Release member 166 is distally biased by a coil spring 168 which ismaintained in axial alignment with the proximal end of release member166 by post 170. The proximal end of coil spring 168 bears against theinner surface of housing cover 120. The distal biasing of release member166 causes pin 172, which extends distally from the distal face ofrelease member 166, to project through an opening formed in the housingbase 119. Compression of obturator assembly 110 relative to cannulaassembly 112 causes release member 166 to be urged in a proximaldirection. This proximal motion of release member 166 urges extendedfinger 162 toward a more vertical orientation, thereby increasing itseffective height and flexing leg portion 154 toward leg 152 and out ofaxial alignment with abutment surface 134a of elongated shield member126, thereby releasing the latching mechanism. As described, in theLander '280 patent, the latching mechanism automatically resets uponreturn of the shield mechanism to its distal-most position.

In a preferred embodiment, the components heretofore described, namelyhousing base 119, housing cover 120, the latching mechanism components,coil spring 140, cylindrical extended portion 138 and elongated shieldmember 126 constitute a first modular subassembly that may beadvantageously manufactured in large quantities and inventoried for useacross a wide range of trocar assembly sizes. As noted hereinbelow,other modular subassemblies may be manufactured to different sizespecifications, e.g., 5 mm, 10 mm, 15 mm, but all would be functionallyoperable with the first modular subassembly disclosed herein.

Referring again to FIGS. 3 and 4, assembly of a second modularsubassembly including knife blade 174 will now be addressed in detail.Knife blade 174 is preferably fabricated from stainless steel by asuitable process, e.g., by metal injection molding. A method for makingmetal injection molded medical instruments is disclosed in commonlyassigned U.S. Pat. No. 5,308,576 to Green et al., the contents of whichare hereby incorporated by reference. Knife blade 174 preferably has acircular base portion 176 which may be hollowed out as shown in FIG. 4or may be formed of a solid material as in knife blade 174' shown inFIG. 4A, such as by machining from a solid block of stainless steel. Thehollowed out embodiment of the knife blade reduces the weight of theknife without affecting the performance characteristics thereof.

A proximally extending elongated portion 178 is provided to facilitatemounting of knife blade 174 to knife rod 180. Elongated portion 178 isprovided with a spindle 182 formed at a proximal end for interfitting ina notch 184 formed near the distal end of knife rod 180. Spindle 182 ismounted to knife rod 180 by inserting spindle 182 through an opening 184formed in the outer surface of knife rod 180 and assuming an abuttingrelation with flange 186 formed in knife rod 180 distal thereof. Ofnote, the features and geometries of knife rod 180 are such that thiscomponent may be manufactured in large quantities to be utilized introcar assemblies, regardless of the diameter of such trocar assembly.Only when the knife rod is joined to a knife blade 174 and a distalshield member 128 is its use limited to a specific trocar assemblydiameter.

Referring now to FIGS. 5-9, once knife blade 174 is mounted to knife rod180, distal shield member 128 functions to maintain knife blade 174 inaxial alignment with knife rod 180. More particularly, as shown in FIGS.6 and 7, the close proximity of the inner wall of distal shield member128 to the point of connection between spindle 182 and knife rod 180prevents separation thereof. Spindle 182 and opening 184 are eachconfigured and dimensioned to permit free rotational movement of knifeblade 174 with respect to knife rod 180, while ensuring and maintaininga fixed relative longitudinal relationship therebetween.

During assembly, knife blade 174 is inserted in knife rod 180, asdescribed above, and the joined components are then passed throughdistal shield member 128 (from the distal end of distal shield member128) at least until stops 190 formed on the outer surface of knife rod180 pass under and proximally of arcuate, inwardly tapered shelf portion192 formed in the inner surface of distal shield member 128 in neckregion 194 thereof. Stops 190 preferably include camming ramps 191 (seeFIG. 7) and the camming interaction between camming ramps 191 and shelfportion 192 causes stops 190 to deflect inwardly, as facilitated by slot193 formed through knife rod 180, to allow stops 190 to pass proximal ofshelf portion 192. Once proximal of shelf portion 192, stops 190 flexback to their original position, thereby preventing distal shield memberfrom sliding distally off of knife rod 180. As thus assembled, a secondmodular subassembly is provided that may be advantageously manufacturedin large quantities and inventoried for use insofar as trocar assembliesrequiring the specific knife/shield diameter are required.

Referring to FIGS. 7 and 7A, longitudinal openings 196 areadvantageously provided in opposite sides of distal shield member 128 topermit inward deflection of stops 190 and separation of distal shieldmember from knife blade 174, if so desired. In this way, reclamation ofindividual components is possible for any reason, e.g., if it isdetermined by manufacturing personnel that knife rod 180 is bestutilized with a different size knife blade/distal shield membercombination. Shelf portion 192 is preferably formed at or near thedistal end of longitudinal openings 196 to facilitate access to stops190. A disassembling forceps-type tool (not pictured) may be provided tofacilitate separation of the components. Thus, the jaws of thedisassembly tool may be maneuvered through opposing longitudinalopenings 196 to compress knife rod 180 such that stops 190 arecompressed to a smaller dimension than shelf 192 to permit stops 190 topass distally below shelf 192.

Relative distal movement of knife blade 174 and knife rod 180 relativeto distal shield member 128 are thus limited by abutment between stops190 and shelf 192. Relative distal movement of distal shield member 128relative to knife blade 174 and knife rod 180 is also limited. Inparticular, distal shield member 128 includes a radially, inwardlydirected abutment flange 131 adjacent tapered portion 129 that isadapted to abut a proximal face 177 of knife blade 174 when distalshield member 128 is in its distal-most position relative to knife blade174 and knife rod 180. When the distal shield member 128 is in itsdistal-most position fins 200 on knife blade 174 are closely adjacent,if not touching, the proximal ends of longitudinal slots 198 formed indistal shield member 128, as discussed in more detail below.

The geometries of and cooperation between knife blade 174 and distalshield member 128 facilitate ease of insertion of modular trocar system100 through a patient's body wall while maintaining surgeon control and,by reason of spring biased distal shield member 128, providing anenhanced margin of safety to internal organs. Referring to FIG. 4 inconjunction with FIGS. 10 and 11, fins 200 define extended cuttingsurfaces 210 which extend beyond the circumference of circular base 176and within slots 198 formed in distal shield member 128. Knife tipportion 212 defines a pyramidal shape having a planar surface 211between each pair of adjacent cutting edges 210. Knife tip portion 212may initially be generally formed by metal injection molding and thecutting edges 210 finely sharpened, for example, by machining and/orpolishing of the surfaces. Extended cutting surfaces 210 preferablyextend radially outwardly to the outer diameter of the cylindricalportion of distal shield member 128, thereby achieving an incision whichapproximates the diameter of the distal shield member 128. By incisingto the diameter of distal shield member 128, the force required forinserting modular trocar system 100 through tissue, such as thepatient's abdominal wall, is reduced.

Referring temporarily back to FIG. 6, a further feature of the modulartrocar system which facilitates ease of insertion into the patient isthat the included angle formed between extended cutting surfaces 210 andthe central longitudinal axis of modular trocar system 100 (asrepresented by section line 8--8 in FIG. 6) is preferably greater thanthe included angle formed between the beveled distal end 214 formed ondistal shield member 128. The included angle formed between extendedcutting surfaces 210 and the central longitudinal axis of modular trocarsystem 100 is represented by the angle "alpha" as measured between thehorizontal surface of fin 200, which is preferably parallel to thecentral longitudinal axis of modular trocar system 100, and the phantomextension of extended cutting surface 210. The included angle formedbetween beveled distal end 214 and the central longitudinal axis ofmodular trocar system 100 is represented by the angle labeled "beta", asmeasured between the horizontal surface of distal shield member 128,which is parallel to the central longitudinal axis of modular trocarsystem 100 and the phantom extension line of beveled distal end 214. Thegreater angle alpha causes an initial displacement of tissue which isadvantageously greater than that required for any portion of modulartrocar system 100 which is proximal of the knife blade 174.

A further feature of the knife blade 174 and the distal shield member128 is the manner in which beveled distal ends 214 of distal shieldmember 128 assume a substantially recessed position relative to fins 210when moved proximally during trocar entry. More particularly, beveleddistal ends 214 define substantially straight edges 215. In addition,the region between circular base 176 and respective fins 210 of knifeblade 174 define recesses 213 within which edges 215 are adapted to ridewhen distal blade member 128 moves proximally relative to knife blade174. Thus, as trocar system 100 is introduced through tissue, theresistance between distal shield member 128 and tissue is minimized bythe nesting of beveled distal ends 214 within recesses 213. Preferably,the thickness of beveled distal ends 214 and the angles of edges 215relative to the angles of fins 210 are such that the nesting orrecessing of beveled distal ends 214 is maximized and penetration forceminimized.

As best illustrated in FIGS. 8 and 9, to facilitate ease of assembly andmodularity, knife rod 180 is provided with a latch portion 188 at aproximal end. Latch portion 188 is in the shape of a ramp so that uponinsertion of knife rod 180 into housing cover 120, latch portion 188 isinitially cammed away from an opening 189 formed in post 144. Uponfurther proximal movement of knife rod 180, latch portion 188 passesthrough opening 189 in post 144 of housing cover 120 and deflects to itsinitial position, thereby locking knife rod 180 with respect to housingcover 120 to prevent relative longitudinal or rotational movementbetween the two components. In addition, distal shield member 128includes a proximal region 133 (of increased inner diameter relative toreduced diameter portion 148 on elongated shield member 126) defining anabutment face 135. When assembled, abutment face 135 contacts shoulder148a on elongated shield member 126 so as to create an interactiveshield mechanism extending substantially the effective length ofobturator assembly 110.

Consistent with the modularity of trocar assembly 100 described herein,an elongated probe type instrument (not shown) may be provided for easyinsertion through opening 146 (FIG. 2) to urge latch portion 188 out ofopening 146. In this way, reclamation of components may be easilyaccomplished if it determines, e.g., that a different knife blade/distalshield member subassembly should be assembled with a given obturatorhousing subassembly.

The rotational relationship of knife blade 174 with respect to knife rod180 and the fixed relationship of knife rod 180 with respect to housingcover 120 facilitates the relative rotational movement of knife blade174 with respect to housing cover 120. Similarly, the rotationalrelationship of proximal region 133 of distal shield member 128 andreduced diameter portion 148 of elongated shield member 126 facilitatesthe relative rotational movement of distal shield member 128 relative toelongated shield member 126 and thus housing cover 120. Accordingly,twisting of housing cover 120 by the user upon insertion of modulartrocar system 100 into the patient does not affect the positioning ofknife blade 174 relative to the patient's body tissue once knife blade174 comes into contact with the tissue.

FIGS. 12 and 13 are useful in illustrating the benefits associated withthe modular aspects of the obturator assembly of modular trocar system100. As shown, each of the components of obturator assembly 110 are thesame except a larger sized knife blade 374 and distal shield member 328have been attached to knife rod 180 and elongated tubular member 180 (ascompared to the trocar system of FIGS. 6 and 8), respectively. Thisinterchangeability of different sized knives and distal shield memberswith standard sized components located proximally thereof obviates theneed to manufacture and inventory both the components and whole units ofnon-modular, conventional trocar systems. In particular, the morecomplex and, therefore, more expensive size-specific elements located inthe obturator housing need not be manufactured and inventoried. Themanufacturer or distributor need only assemble the appropriate sizedknife and distal shield member with the otherwise standard sized controlcomponents as demand dictates.

Referring now to FIGS. 14-17, cannula assembly 112 of modular trocarsystem 100 will now be described in greater detail. Cannula assembly 112includes a molded cylindrical base portion 216 having transverselyextending grip portions 218 formed to extend form an annular flangeformed at the proximal end of cylindrical base 216. A series of slots222 are formed along the underside or distal side of grips 218.

Slots 222 are particularly advantageous in two respects. First, inassembling cannula assembly 112, there are three basic principlecomponents: cylindrical base portion 216 having outwardly directingfinger grips 218, a duck bill valve element 224 having a flange 226which is configured and dimensioned to rest on annular flange 220 ofcylindrical base portion 215 and a cannula housing cover portion such asproximal housing element 228 which is configured and dimensioned to reston duck bill flange 226 and within the outwardly directed finger grips218. It has been found that by coring out the underside of outwardlyextending finger grips 218 with parallel slots 222, molding sinks whichhad been previously forming on the proximal side of outwardly extendingfingers 218 of cylindrical base portion 218 were significantly reduced,thereby providing a much more reliable flat surface, as best shown inFIG. 17, against which duck bill flange 226 may rest and against whichthe upper or proximal housing element 228 may be welded.

This greater cooperation between the two cannula housing elementsreduces the force which must be applied as between the two housingelements during the welding process, thereby reducing the likelihoodthat the duck bill valve 224 will be torqued. Torquing of the duck billvalve 224 can potentially reduce the sealing function of the element inthe absence of a surgical instrument inserted therethrough.

The second respect in which slots 222 are advantageous is that on theunderside of the cylindrical base portion 216 is normally the placewhere the user grips the cannula the cylindrical base portion 216.Accordingly, the slots provide an improved gripping surface to the user.

A further feature of cannula assembly 112 is the provision of adetachable cannula 116 which readily connects and disconnects fromcylindrical base portion 216. Cannula 116 is preferably molded with asubstantially constant inner and outer diameter. However, cannula 116preferably includes a slightly larger inner diameter at its proximalend, e.g., of 2-3 cms length, to facilitate introduction ofinstrumentation, and a tapered outer diameter at its distal-mostportion, e.g. over the distal-most 2-3 cms of length, the tapered outerdiameter being largest at a proximal end thereof and smallest at adistal end thereof. In this way, molding is facilitated whilepenetration force is minimized by reducing the outer diameter of cannula116 in the region where tissue first makes contact and by providing agradual taper to the outside diameter to assist in dilation of tissue asit passes proximally along the outer wall of cannula 116.

An elastomeric O-ring 230 is interposed between cylindrical base portion216 and cannula 116 to maintain a fluid-type seal between cannula 116and cylindrical base portion 216. Cannula 116 is formed of apredetermined diameter so as to form a longitudinal throughbore 232 incommunication with a passageway formed through cylindrical base portion216 and proximal housing element 228. Cannula 116 is further providedwith an annular flange 234 which is particularly sized to be received inthe distal end of cylindrical base portion 216. Flange 234 is preferablya standard size such that cannulas having different sized diameterpassageways formed therethrough may be formed with a flange that has thesame configuration and dimension as flange 234. In this manner, cannulasof varying sized and dimensions may be interchangeably attached to agiven cylindrical base portion such cylindrical base portion 216.

To facilitate the interconnectability of cannula 116 and cylindricalbase portion 216, a quick connect mechanism is provided which, forexample, may be by a series of engageable mating members 236 formed oncannula 116 proximal of flange 234 which interconnect cannula 116 withcylindrical base portion 216 by way of a series of mating indentedsurfaces 238 formed along the inner wall of cylindrical base portion216. The two elements are brought into engagement with each other byinserting the proximal end of cannula 116 into the distal end ofcylindrical base portion 216 and rotating cannula 116 clockwise untilmating members 236 engage and lock into mating surfaces 238. The twoelements may be disengaged by applying a proximally directed force tothe cannula toward cylindrical base portion 216 and rotating cannula 116counterclockwise. This feature is particularly advantageous duringmanufacture and assembly of cannula assembly 112 in that it facilitatesinventory management and manufacturing efficiencies due to thecylindrical base portion 216 now being a single component which is ableto be utilized across multiple cannula diameter products, the onlydifference being the cannula which is ultimately secured to thecylindrical base portions at the final stage of manufacture.

Also provided on cannula assembly 112 is a seal assembly 240 whichgenerally includes a housing 242, a seal member 244 and a plurality ofspreading members (not shown) which serve to spread an orifice 246 ofthe seal member to accommodate instruments of different diameterstherethrough while maintaining a fluid-tight seal. A similar sealassembly is commercially available with the VERSAPORT™ trocar systemmanufactured by United States Surgical Corporation, Norwalk, Conn.

Referring to FIG. 18, the interchangeability of different sized cannulaswith the same sized housing is illustrated by smaller cannula 316 shownattached to cannula 216. This feature greatly simplifies the problem ofmanufacturing and keeping an inventory of numerous different diametercannula assemblies.

It will be understood that various modifications may be made to theembodiments disclosed herein. Therefore, the above description shouldnot be construed as limiting, but merely as exemplifications ofpreferred embodiments. Those skilled in the art will envision othermodifications within the scope and spirit of the claims appended hereto.

What is claimed is:
 1. A method of assembling an obturator assembly foruse in a trocar system comprising the steps of:connecting a shieldmember of a first predetermined configuration and dimension to a firsthousing section; attaching a knife blade assembly of a secondpredetermined configuration and dimension to the first housing sectionwith a single motion wherein the attachment permits rotation of theknife blade relative to the first housing section; and attaching thefirst housing section to a second housing section with a quick connectmechanism which includes first and second mating portions such that thefirst and second housing sections are movable from a spaced apartposition to a connected position in a single motion.
 2. A method ofassembling a trocar system, comprising the steps of:connecting a firsthousing which includes a valve assembly disposed in a passageway formedbetween an open proximal end and an open distal end, with a cannulawhich defines a passageway of a predetermined size therethrough;connecting a shield member of a first predetermined configuration anddimension to a second housing section; attaching a knife blade assemblyof a second predetermined configuration and dimension to the secondhousing section with a single motion wherein the attachment permitsrotation of the knife blade relative to the second housing section;attaching the second housing section to a third housing section with aquick connect mechanism which includes first and second mating portionssuch that the second and third housing sections are movable from aspaced apart position to a connected position in a single motion; andinserting the shield member and knife blade assembly into the openproximal end of the first housing such that at least a portion of theshield member extends through the cannula.
 3. The method according toclaim 2, wherein the step of connecting the first housing to the cannulaincludes aligning a third mating portion, formed on the first housing,with a fourth mating portion, formed on the cannula, and moving thefirst housing and the cannula from a spaced apart relative orientationto an attached orientation, wherein the third and fourth mating portionsare engaged.
 4. The method according to claim 3, which further comprisesthe step of forming a fluid-tight seal between the first housing and thecannula.